Residual pyrethroid content in wet and dry interior decorative coatings- an HPLC study

Johani, Joshua Tinashe (2020-12)

Thesis (MSc)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: Mosquitoes knownto be malaria vectors continue to affect many regions in Africa.To mitigate the detrimental health effects arising from the cohabitation of such species with humans, pyrethroid-based interior decorative coatings are being developed. The paints are seen as a viable option to improve the longevity of the insecticides. However,before the insecticidal paints can find widespread application, there is need for the development of analytical methodsto quantify the levels of pyrethroid insecticides in the paint.The analytical information is important to determine the qualityof the product and the safety profile of the insecticidal paint to humans and the environment.A normal phase HPLC method was developed for the rapid identification and quantification of bifenthrin, cis-and trans-permethrinbased on available analytical standards. A multiple point matrix-matched calibrationapproach was employed for the determination of insecticide quantities. The limitsof quantification forthe method are 5.8ng for bifenthrin, 4.4 ng for cis-permethrin and 5.0 ng for trans-permethrin. The recoveries for the analytes are >99 % and the relative standard deviations are below 2%. Therefore,the validation data for the method are excellent. In the next step, a method was developed to isolate the insecticides from the matrix of complex paint formulations. A3 hours Soxhlet extraction protocol with dichloromethane-hexane(95:5 (v/v))was found to be suitablefor the isolation of permethrin and bifenthrin from the paint matrix prior to HPLC analysis. The method can be applied directly to paint films. Wet paints are required to spread over 5 g sand+ 0.1 g LiBr and 2.5 g MgSO4for efficient extraction. The extraction efficiencies are between 86-96 % bifenthrin and 88-99%permethrin. The relative standard deviationsare acceptable and below 20 %.The new developed method was successfully applied in the analysis of real insecticide paints.Preliminary studiesshow that decorative coatings may contain >30 % of the initial pyrethroid content after more than 2 yearsof application. This is remarkable and very promising for the application ofpyrethroid paints in contributing towards the fight against malaria.

AFRIKAANSE OPSOMMING: Malaria, en muskiete wat die parasiet dra, raak steeds baie streke in Afrika. Om die nadelige gevolge van die saamwoon van sulke spesies te versag word daar piretroïed-gebasere verwe ontwikkel. Die verf word gesien as 'n lewensvatbare opsie om die langlewendheid van die insekdoders te verbeter. Voordat die insekdodende verf wydverspreide toepassing kan vind is dit nodig om analitiese metodes te ontwikkel om die vlakke van piretroïed-insekdoders in die verf te kwantifiseer. Die analitiese inligting is belangrik om die kwaliteit van die produk en die veiligheidsprofielvan die insekdodendeverf vir mense en die omgewing te bepaal.'n Normale-fase hoëdrukvloeistofchromatografie-metode (HPLC) is ontwikkel vir die vinnige identifikasie en kwantifisering van bifentryn, cis-en transpermetrien gebaseer op beskikbare analitiese standaarde. 'n Meervoudige punt-matriks-gekalibreerde benadering is gebruik vir die bepaling van die hoeveelheid insekdoders. Die kwantifiseringsgrense virdie metode is 5.8 ng vir bifentryn, 4.4 ng vir cispermetrien en 5.0 ng vir transpermetrien. Herstel vir die analiete is >99 % en die relatiewe standaardafwykings is onder 2 %. Die bevestigingsdata vir die metode is dus uitstekend.In die volgende stap is 'n metode ontwikkel om die insekdoders uit die komplekse matriks formulering te isoleer. Daar is gevind dat 'n 3 uur Soxhlet-ekstraksieprotokol met dikloormetaan-heksaan (95:5 (v/v)) geskik is vir die isolasie van permetrien en bifentryn vanaf die verfmatriks voor HPLC-analise. Die metode kan direk op verffilms toegepas word. Nat verf is nodig om oor 5 g sand + 0.1 g LiBr en 2.5 g MgSO4te versprei te word vir effektiewe ekstraksie. Die ekstraksie-doeltreffendheid is tussen 86 –96 % bifentryn en 88 –99 % permetrien. Die relatiewe standaardafwykings is aanvaarbaar en onder 20 %.Die nuut-ontwikkelde metode is suksesvol toegepas in die ontleding van regte insekdoderverf. Voorlopige studies toon dat dekoratiewe bedekkings na meer as 2 jaar nog >30 % van die aanvanklike piretroïedinhoud kan bevat. Dit is merkwaardig en baie belowend vir die toepassing van piretroïedverf se bydra tot die stryd teen malaria.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/109272
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